Ladder for floating-roof tanks



April 1930. O B. o. BUSHNELL 1,754,384

LADDER FOR FLOATING ROOF TANKS Filed Au '15, 1927 IN VEN TOR.

BONE 1x52222922 A TTORNEY.

Patented Apr. 15, 1930 UNITED STATES PATENT OFFICE BURDGE OGDEN BUSHNELL, OF LOS ANGELES, CALIFORNIA, ASSIGNOR T UNION OIL COMIANY OF CALIFORNIA, OF LOS ANGELES, CALIFORNIA, A. CORPORATION OF CALIFORNIA LADDER FOR FLOATING-ROOF TANKS Application filed August 15, 1927. Serial No. 213,018.

This invention relates to ladder constructions and particularly to those intended for use in tanks having floating roofs which rise and fall with the liquid level therein.

The object of the invention is to provide a ladder of this type the construction of which will permit the lowering into the tank of whatever length of'ladder is required for use in the tank at any time according to the vary ing demands occasioned by the movements of the floating roof, and whose construction shall be such that those portions contained in the tank will be rigidly positioned therein, while the surplus portion not required in the tank may be readily disposed elsewhere. A further object is to render such positioning of the parts for such uses entirely automatic and to control such automatic movement by the rising and falling movements of the floating roof. A further object is to permit easy removal of the ladder construction from the tank for repair thereof and to make the parts easily accessible at all times.

Briefly stated the invention in one of its broadest aspects comprises a plurality of flexibly connected treads in combination with means for normally maintaining the treads in rigid relation both longitudinally and transversely of the ladder, the treads being spaced longitudinally. The invention also comprises the combination of such a flexible structure and its rigidifyingmeans, with a tank having a floating roof. In a preferred form. rigid spacers are provided between the treads, and flexibility is obtained by pivotally connecting the spacers with the treads. In such a case, longitudinally extending rigid means such as posts or other rigid guidea'are provided for engagement by the treads in or 'der to maintain the rigid relation. Preferably, the posts are secured to the bottom of the tank and pass upward through stufling boxes in the floating roof, the post portions above the roof being slidably engaged by the treads whereby said treads are pushed upward along the posts as the roof rises, said treads being positively pulled downward therealong as the roof falls, by reason of positive connection of the lowermost tread with the roof. The invention further comprises guiding means over which the surplus portion of the flexible tread structure passes in order that said surplus may depend outside the tank when the roof is elevated and whence it may be drawn back into the tank when the roof descends.

In the accompanying drawings wherein certain embodiments of the invention are disclosed by way of illustration,

Fig. 1 is chiefly a side elevation showing the ladder of the present invention installed in a floating-roof tank;

Fig. 2 is a face view thereof, being taken at right angles to that of Fig. 1;

Fig. 3 is a plan view;

Fig. 4C is a cross-sectional detail taken on the line H of Fig. 2;

Fig. 5 is a sectional detail taken on the line 55 of Fig. 2;

Fig. 6 is an elevational detail showing the joints between the ladder parts and showing the1r relation when in operative position; and

Fig. 7 is an elevation showing a modified form of guide for the upper part of the flexible structure.

The drawings disclose a tank 10 which may be provided with a wind girder 12 at its top and which contains a floating roof 14: carrying any suitable type of seal 15 between it and the tank walls. A pair of vertical standards or guides in the form of posts 16 having their lower ends secured at 18 to the bottom of tank 10, pass upwardly through stuifing boxes 20 and floating roof 14 and as shown have their upper ends tapered as indicated at 21, said ends terminating adjacent the side rails 22 of a super-structure to which rails said upper ends are secured by means of brackets 24. Said rails are supported by a frame 25 which is secured to the outer side of the tank wall and which includes suitable braces 26, this structure also carrying a platform 27 by means of which the ladder maybe reached, access to said platform being had bv way of any suitable stair 28 or the like. The rails 22 support a pair of discs or sprockets 30 carried by shafts 32 journaled at 33, said discs 30 being notched at 34, if desired, for the reception or" the treads 35 as best indicated in Figs. 1 and 3, or the discs may be smooth.

The treads are in the form of rungs or bars having at their ends open eyes or yokes 36 which engage around the posts 16 and are adapted to slide up and down therealong, openings 38 between the jaws of said yokes being provided to pass the brackets 24 which position the upper ends of said posts. Rigid spacers 40 are disposed between the treads 35 and are flexibly connected at one end with adj acent treads through the medium of a pivotal locking connection comprising flattened portions 42 on each tread 35 which portions receive eyes 44 on the respective ends of the spacers 40, said eyes having on one side openings 45 which are wide enough to pass said flattened portions 42 when moved to positions at right angles to the normal operating position indicated in the various figures, said openings 45 however being narrower than the normal diameter of said treads so that said open eyes 44 will not become disengaged from their respective treads when the parts are in operative position. Thus this connection constitutes locking means for normally retaining the parts in such position. The opposite end of said spacer 40, in the preferred form, is rigidly secured to the respective tread 35 as by means of welding as indicated at 46 (Fig. 6), this welded joint lying alongside of the joint formed by engagement of the corre-- sponding open eye 44 at the flattened portions 42. This construction of tread 35 with its spacers 40 forms a sort of. link, and in order that these links or ladder sections may be uniform in construction each spacer 40 is offset as indicated at 48 whereby the eyes 44 are aligned throughout the ladder length and the welded joints 46 are similarly aligned.

The link construction as above described with its treads 35 and ri id spacers 40, thus provides a structure whic when rigidly held in vertical alignment by means of posts 16, causes the up er treads to be supported by the lower treads due to the rigidity of said spacers 40. The welded joint 46 causes the spacers 40 to hold treads 35 against rotation and thereby prevents the eyes 36 from binding on the posts 16 during movement. The lower-most tread 35 is supported upon and connected with the tank 14 by means of connecting and spacing links 50 whose lower ends are fixed on brackets 52 secured to the roof and whose upper ends are pivotally connected with the bottom tread 35 by means of eyes 54 which may be like eyes 44 and may be similarly mounted on the tread.

From the foregoing, it will be seen that as the floating roof 14 falls, the links 50 will cause the treads 35 and their spacers 40 to be pulled downward along guide posts 16, and as the roof rises said treads and their spacers will be pushed upward along said posts 16, those treads which extend beyond the upper ends of the osts being allowed to break or swing at their joints and roll over the discs 30, proper movement being insured by means of weights W which are connected with the outermost tread 35 by means of links 55, whereby any slack which may tend to occur between the discs 30 will be taken up. The tapered upper ends 21 of the guide posts 16 in conjunction with wheels 30 are ample to positively guide the open eyes or yokes 36 into position on said posts 16 when the roof 14 falls and draws the ladder down into the tank. Thus, the vertical height of the link ladder portion which descends into the tank is always substantially equal to the distance between roof 14 and platform 27 regardless of the position of the roof.

In Fig. 7 a slight modification is disclosed wherein the wheels 30 are replaced by extensions 16' of the guide posts 16, these extensions being curved as shown for the purpose of carrying the eyes 36 and treads 35 to a position outside the tank, extensions 25 provided with brackets 24' being provided beyond the framework 25 to position each of the curved guides 16. In order to insure proper return of said eyes36 to the tapered ends 21, a suitable guide sleeve 56 carried by arm 58 on the framework 25 may be positioned about said tapered end 21'.

An attendant may reach the ladder for the purpose of descending into the tank by ascending the stair 28 to the platform 27 and passing along the platform to a point adjacent the ladder, the position of that portion of the ladder within the tank being the same regardless of the position of the floating roof. The rigidity of the posts 16 imparts rigidity to the link structure formed by treads 35 and their spacers 40, and ermits descent by the attendant without wab ling or wavering of the ladder. By disconnecting the links 50 which secure the bottom tread to the roof 14, the entire link structure may be easily withdrawn from the tank for inspection, replacement or repair. A decided advantage of the present construction resides in the fact that it is not necessary to support from the super-structure the effective portion of the ladder within the tank and the weight of the attendant thereupon, this being eliminated by means of the rigid spacers 40 through the medium of which the weight imposed upon the ladder is supported by the roof.

While the forms described and shown represent desirable embodiments of the inventermediate points of the spacers so that flexible connections would occur only at alternate or other selected treads instead of at every tread. Therefore, it is to be understood that the above disclosures are-merely illustrative of the generic invention and are not ill) to be considered as limiting, many variations being possible within the scope of the following claims.

I claim:

1. A ladder comprising a rigid portion and a flexible portion, the flexible portion being adapted to be longitudinally slidably mounted upon the rigid portion and comprising treads having rigid spacers therebetween, to produce a structure which is rigid throughout when assembled.

2. A ladder comprising a plurality of swingingly connected rigid sections, means for normally holding said sections rigidly in alignment and means with respect to which said ladder is movable for collapsing upper sections thereof.

3. A ladder comprising a plurality of swingingly connected rigid sections, and means for normally maintaining said sections rigidly in alignment, said ladder being bodily movable with respect to said means to permit swinging of upper sections of the ladder.

4. A ladder comprising a plurality of swingingly connected rigid sections, means for normally holding said sections in rigid alignment and means across which certain sections of said ladder are movable to break said certain sections.

5. Incombination, a ladder comprising a plurality of flexibly connected sections, elevated means associated with the ladder and with respect to which the ladder is bodily movable to permit upper sections of the ladder to break and means for maintaining lower sections of the ladder in rigidly extended condition.

6. In a ladder, a plurality of transverse treads, rigid spacers there between having flexible connection therewith, and means continuously extending longitudinally of the lad der adaptedto maintain a plurality of treads in fixed relation.

7. In a ladder, a plurality of flexibly connected treads in combination with means for spacing said treads rigidly apart longitudinally of the ladder and means continuously extending longitudinally of the ladder for normally maintainingthe treads in rigid rela- 2* tion to one another transversely of the ladder.

8. A ladder comprising a plurality of transverse treads, rigid spacers therebetween, flexible connection between certain of said spacers and certain treads, and means contin uously extending longitudinally of the ladder adapted to maintain a plurality of treads in fixed relation longitudinally of the ladder whereby upper treads are supported by lower treads.

9. A ladder comprising a plurality of treads, rigid spacers between said treads and flexibly connected therewith, guides for maintaining a plurality of treads in fixed relation to one another, a base connected with said guides and a fixed connection between the base and a lower tread.

10. A ladder comprising a plurality of treads, rigid spacers disposed between said treads and having flexible connection therewith, means for maintaining a plurality of treads in fixed relation to one another, and means for locking said spacers upon said treads when in such fixed relation and permitting their separation when in another position.

11. A ladder comprising a plurality of flexibly connected sections, each section comprising a tread and a rigid spacer, and elongated rigid guides engaged by the treads and along which said treads are adapted to move longitudinally of the ladder.

12. A ladder comprising a plurality of fiexibly connected sections, each section comprising a tread and a rigid spacer, and elongated guides engaged by the ends of the treads and upon which said ends are adapted to travel.

13. A ladder comprising a plurality of treads, rigid spacerstherebetween, one end of each spacer being rigidly connected with a tread and the other end being flexibly connected with another tread, means for locking said spacers against removal from the treads to which they are connected and means for maintaining a plurality of treads in fixed relationship longitudinally of the ladder.

14. A ladder comprising a plurality of treads, rigid spacers connected with said treads, said spacers being flexibly connected with certain of said treads, longitudinally extending means engaged by said treads for maintaining longitudinal alignment of the treads, and guiding means adapted to receive said treads from said longitudinally extending means and around which said treads and spacers are adapted to pass by reason of said flexible connections whereby treads may pass over said guiding means and depend there from. I

15. A ladder according to claim 14 wherein a weight is provided on the said depending end for absorbing slack.

16. In combination a walled structure, a flexible sectional ladder to be raised and lowered in, said structure, and means associated with the structure and cooperating with the ladder for automatically placing lower sections of the ladder in rigid condition as the ladder is lowered in the structure.

17. In combination, a tank, a flexible sectional ladder structure to be lowered into the tank, guide means upon the upper edge of the tank over which the ladder structure passes as it moves into the tank, and means carried by the tank and cooperating with the ladder structure whereby the ladder is rendered rigid when lowered into the tank.

18. In combination, a tank, upright positioning means in the tank, guide means on the upper edge of the tank, and a sectional flexibly connected ladder adapted to be passed over said guides into engagement with said positioning means, said positioning means being adapted to align the ladder sections in longitudinally rigid relation.

19. In combination a ladder, a base, means for connecting the ladder to said base, said ladder comprising pivotally connected sections, means for maintaining said ladder in rigid extended position above said base and below an upper limit, and means with respect a to which said ladder moves bodily and operatively associated with said ladder to break the ladder sections above said upper limit.

20. In combination a ladder, a base, means for connecting the ladder to said base, said ladder comprising pivotally connected sections, means for maintaining said ladder in rigid extending position above said base and below an upper limit and means with respect to which said ladder moves bodily and operatively associated with said ladder to break the ladder section above said upper limit, said last mentioned means being also operable to permit the ladder sections which have been broken to reassume a rigid extended position on movement of said ladder.

21. In combination a tank, a floating roof for said tank, a ladder comprising a plurality of flexibly connected sections, the ladder being connected with said roof, elevated means associated with the tank and with respect to which the ladder moves bodily to permit upper sections thereof to swing, and means for maintaining those sections between the roof and the elevated means in ri id condition.

22. In combination a tan having a floating roof, a platform at the top of the tank, aflexible ladder connecting with said roof and extending upward to said platform, and guide means on said platform over which said flexible ladder is adapted to pass as the roof rises and falls.

23. In combination, a floating roof tank, a platform at the top of said tank, a ladder having treads, said ladder being connected to the floating roof and extending to said platform, means for maintaining the distance between treads below said platform substantially constant, and means for maintaining the Vertical height of said ladder substantially equal to the distance between said roof and said platform irrespective of the position of the roof and in rigid condition.

24. In combination, a floating roof tank, a platform at the top of said tank, a ladder connected to said roof and having treads, means for maintaining the distance between treads of the ladder substantially constant and means for maintaining all of the ladder portion between the roof and platform in extended condition and the vertical height of the ladder substantially equal to the distance from the roof to the platform irrespective of the position of the roof.

25. In combination a tank, a floating roof therein, upright guides supported on the bottom of said tank and extending through said roof, and transverse ladder'treads mounted above said roof to move on said guides.

26. A construction according to claim 25 wherein rigid spacers are disposed between the adjacent treads.

27. A construction according to claim 25 wherein rigid spacers extend between adjacent treads and said spacers are flexibly connected with said treads.

28. A construction according to claim 25 wherein the lowermost tread is secured to said floating roof.

29. In combination a tank, a floating roof therein, upright guides supported on the botof the tank and extending through said roof, transverse ladder treads mounted above said roof to move on said guides, rigid spacers disposed between adjacent treads and flexibly connected therewith, and means adapted to receive treads and spacers from said guides and about which said spacers are adapted to bend by reason of said flexible connections whereby treads and spacers received by said means may depend therefrom.

30. A construction according to claim 29 wherein the lowermost tread is positively connected to said roof.

Signed at Los Angeles, in the county of Los Angeles and State of California, this 28th day of July A. D. 1927.

BURDGE OGDEN BUSHNELL. 

